<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        var name;
        name = 'tom';

        var age = 13;

        sex = 'male'; // 强烈不建议

        var a = 5, b = 6, c;
        // alert(sex);


        {
            var x = 6;
            let  y = 8; // 支持块级作用域
        }

        // alert(x)
        alert(y)

    </script>
</head>
<body>

</body>
</html>